| /* |
| * Copyright (c) 2003, 2006, Oracle and/or its affiliates. All rights reserved. |
| * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
| * |
| * This code is free software; you can redistribute it and/or modify it |
| * under the terms of the GNU General Public License version 2 only, as |
| * published by the Free Software Foundation. |
| * |
| * This code is distributed in the hope that it will be useful, but WITHOUT |
| * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
| * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
| * version 2 for more details (a copy is included in the LICENSE file that |
| * accompanied this code). |
| * |
| * You should have received a copy of the GNU General Public License version |
| * 2 along with this work; if not, write to the Free Software Foundation, |
| * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
| * |
| * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
| * or visit www.oracle.com if you need additional information or have any |
| * questions. |
| * |
| */ |
| |
| #include "salibelf.h" |
| #include <stdlib.h> |
| #include <unistd.h> |
| #include <string.h> |
| |
| extern void print_debug(const char*,...); |
| |
| // ELF file parsing helpers. Note that we do *not* use libelf here. |
| int read_elf_header(int fd, ELF_EHDR* ehdr) { |
| if (pread(fd, ehdr, sizeof (ELF_EHDR), 0) != sizeof (ELF_EHDR) || |
| memcmp(&ehdr->e_ident[EI_MAG0], ELFMAG, SELFMAG) != 0 || |
| ehdr->e_version != EV_CURRENT) { |
| return 0; |
| } |
| return 1; |
| } |
| |
| bool is_elf_file(int fd) { |
| ELF_EHDR ehdr; |
| return read_elf_header(fd, &ehdr); |
| } |
| |
| // read program header table of an ELF file |
| ELF_PHDR* read_program_header_table(int fd, ELF_EHDR* hdr) { |
| ELF_PHDR* phbuf = 0; |
| // allocate memory for program header table |
| size_t nbytes = hdr->e_phnum * hdr->e_phentsize; |
| |
| if ((phbuf = (ELF_PHDR*) malloc(nbytes)) == NULL) { |
| print_debug("can't allocate memory for reading program header table\n"); |
| return NULL; |
| } |
| |
| if (pread(fd, phbuf, nbytes, hdr->e_phoff) != nbytes) { |
| print_debug("ELF file is truncated! can't read program header table\n"); |
| free(phbuf); |
| return NULL; |
| } |
| |
| return phbuf; |
| } |
| |
| // read section header table of an ELF file |
| ELF_SHDR* read_section_header_table(int fd, ELF_EHDR* hdr) { |
| ELF_SHDR* shbuf = 0; |
| // allocate memory for section header table |
| size_t nbytes = hdr->e_shnum * hdr->e_shentsize; |
| |
| if ((shbuf = (ELF_SHDR*) malloc(nbytes)) == NULL) { |
| print_debug("can't allocate memory for reading section header table\n"); |
| return NULL; |
| } |
| |
| if (pread(fd, shbuf, nbytes, hdr->e_shoff) != nbytes) { |
| print_debug("ELF file is truncated! can't read section header table\n"); |
| free(shbuf); |
| return NULL; |
| } |
| |
| return shbuf; |
| } |
| |
| // read a particular section's data |
| void* read_section_data(int fd, ELF_EHDR* ehdr, ELF_SHDR* shdr) { |
| void *buf = NULL; |
| if (shdr->sh_type == SHT_NOBITS || shdr->sh_size == 0) { |
| return buf; |
| } |
| if ((buf = calloc(shdr->sh_size, 1)) == NULL) { |
| print_debug("can't allocate memory for reading section data\n"); |
| return NULL; |
| } |
| if (pread(fd, buf, shdr->sh_size, shdr->sh_offset) != shdr->sh_size) { |
| free(buf); |
| print_debug("section data read failed\n"); |
| return NULL; |
| } |
| return buf; |
| } |
| |
| uintptr_t find_base_address(int fd, ELF_EHDR* ehdr) { |
| uintptr_t baseaddr = (uintptr_t)-1; |
| int cnt; |
| ELF_PHDR *phbuf, *phdr; |
| |
| // read program header table |
| if ((phbuf = read_program_header_table(fd, ehdr)) == NULL) { |
| goto quit; |
| } |
| |
| // the base address of a shared object is the lowest vaddr of |
| // its loadable segments (PT_LOAD) |
| for (phdr = phbuf, cnt = 0; cnt < ehdr->e_phnum; cnt++, phdr++) { |
| if (phdr->p_type == PT_LOAD && phdr->p_vaddr < baseaddr) { |
| baseaddr = phdr->p_vaddr; |
| } |
| } |
| |
| quit: |
| if (phbuf) free(phbuf); |
| return baseaddr; |
| } |